DFNB3 mutations result in recessive nonsyndromic profound congenital hearing impairment. The map position of DFNB3 was refined to 17p11.2 (Liang et al. 1998) and its mouse homolog, shaker2, were functionally cloned. DFNB3 and shaker2 encodes a novel unconventional myosin gene, myosin XV. Myosin-15 represents a new branch of the unconventional myosin family. The function of this gene product in the auditory system is unknown and is being studied in the LMG. The genomic and cDNA structures of the human (MYO15) and mouse (Myo15) myosin XV genes have now been elucidated. The full-length cDNAs are ~ 12 kb and contain open reading frames derived from 66 exons. The encoded proteins are 87 % similar and have predicted molecular masses of ~ 380 kDa. Analysis of RT-PCR products indicates that additional myosin-15 several isoforms result from alternative splicing. Ongoing expression studies suggest that myosin XV transcription may be restricted to relatively few cell types in the auditory system and in the anterior pituitary. In mice, this finding was confirmed and extended by in situ hybridization studies which revealed Myo15 transcripts in cells of the developing cochlea and vestibular organ. As an additional and important tool to study myosin-15 expression and function, rabbit polyclonal anti-Myo15 antibodies have been raised against two synthetic and two recombinant peptides. Preliminary analysis indicates that antibody production against all of the peptides was successful. In collaboration with Dr. Bechara Kachar, the Myo15 antibodies will also be used to examine the ultra-structural location of Myo15 in the inner ear at the level of electron microscopy. The goal of this project is to understand the role of myosin V in the auditory system and in the pituitary. - DFNB3, mutations of MYO15, function of MYO15, gene structure, isoforms, electron-microscopy, deafness, hearing impairment - Human Subjects & Human Subjects: Interview, Questionaires, or Surveys Only